During surgical implantation of femoral condylar prostheses, it is typically necessary to utilize some type of tool to gauge whether or not the distal aspect of the femur has been properly sized to receive the condylar implant. This gauge typically resembles the actual prosthesis which will be implanted. The surgeon first "resects" the surface of the bone to match the geometry of the implant by making several cuts as shown, for example, in U.S. Pat. No. 4,474,177 to Whiteside, the entire disclosure of which is expressly incorporated by reference herein and relied upon.
Once the distal aspect of the femur has been resected, a convex patellar groove is formed in the anterior surface of the resected bone, in order to accommodate the mating concave patellar track of the condylar implant. In a total knee replacement, the external distal surface of the condylar implant, including that of the patellar track, articulates with the proximal aspect of an implanted tibial component. A previously devised cutting guide for shaping the patellar groove is the subject of allowed U.S. patent application Ser. No. 462,268, filed Jan. 9, 1990 and assigned to the instant assignee, the entire disclosure of which is expressly incorporated by reference herein and relied upon. Depending upon the degree of knee reconstruction indicated, a patellar prosthesis may also be implanted as shown, for example, in U.S. patent application Ser. No. 466,093, filed Jan. 12, 1990 and also assigned to the present assignee, the entire disclosure of which is expressly incorporated by reference herein and relied upon.
A challenge confronted by condylar implant systems is the need to both accurately form a patellar groove in the resected surface of the distal femur and perform a trial reduction of the knee joint to ascertain proper sizing of the condylar implant. This is conventionally a sequential procedure employing first a guide seated on the resected bone for engaging a shaping tool which forms the patellar groove in the bone. Secondly, a trial condylar implant is seated on the resected surface of the distal femur, having a size and shape resembling that of the permanent condylar prosthesis actually being implanted, after which the trial reduction of the knee is performed by articulating the femur and tibia. Following satisfactory trial reduction, the trial implant is removed and replaced by the permanent condylar implant. A disadvantage of the procedure set forth above is degradation of the bone caused by alternate insertion and removal of separate track cutting and trial implant guides, respectively. Moreover, use of separate track cutting and trial implant guides is relatively inefficient and time-consuming, further complicating the surgical procedure for reconstructing the knee joint.
U.S. Pat. No. 4,721,104 to Kaufman and Whiteside, describes a femoral shaping apparatus employing a template having a straight slot therein for cutting a relatively deep recess for an intercondylar stabilizing housing of a knee implant. The patented system also describes a trial implant module, however, it does not disclose a cutting guide having a curved track useful for forming a groove to accommodate a patellar track on such a prosthesis.
Allowed U.S. patent application Ser. No. 666,153, filed Mar. 3, 1991 and assigned to the instant assignee, shows using common surgical instrumentation to form both a groove and deep recess in the resected distal femur, respectively accommodating a patellar track and intercondylar stabilizing housing of the implant, but does not disclose a modular system also capable of performing a trial joint reduction. U.S. patent application Ser. No. 666,160, filed Mar. 7, 1991 and also assigned to the instant assignee, shows a device and method which combine the features of a femoral trial implant and patellar track cutting guide, so that the patellar groove may be shaped and a surgical trial reduction of the total knee joint accurately performed using common instrumentation. However, this patent does not show how such modular instruments could be modified to also form a deep recess in the distal femur to accommodate the intercondylar housing of a posterior-stabilized femoral component.
Accordingly, there remains a need for modular instrumentation which can be employed to form both a patellar groove and deep recess in the resected surface of a distal femur using a common guide which also functions to perform a trial reduction of the total knee joint.